🚀 go-pugleaf

Does anyone know of a bulletproof way for a TSR to tell whether DOS (assume
2.x or 3.x) is idling in the command interpreter, or executing a program?

I have determined, through much pain and disassembly, that DOS uses service
0A (buffered string input) to get the next command, but other programs use that
as well.  I can get by on this knowledge, but I would prefer something a little
more certain.

For the record, I am writing a screen-saver TSR that will only trigger when DOS
is idling.  There are dozens of screen-savers, but I need one that won't kill
a lengthy graphics program.  (Ever try generating the Mandelbrot set on a 4.77 
MHz XT with no FPU?  I thought so.)

Any leads will be duly appreciated.

				paul